This is the city's oldest monument and the only intact example of Almoravid architecture in all of Morocco (the few other ruins include some walls here in Marrakesh and a minaret in El Jadida). Dating from the 12th century, this masterpiece of mechanical waterworks somehow escaped destruction by the Almohads. It was once used for ablutions before prayer in the next-door Ali ben Youssef Mosque (relying on the revolutionary hydraulics of khatteras, drainage systems dug down into the water table), and also had a system of toilets, showers, and faucets for drinking water. It was only excavated from the rubble of the original Ali ben Youssef Mosque and Medersa in 1948. The monument is in an advanced state of disrepair and in 2014 was closed to the public for safety reasons. You can view it from the exterior perimeter.
Pl. Ben Youssef, Marrakesh, Morocco